Inorganic fiber board with binder of thermosetting resin and thermoplastic vinylic resin

ABSTRACT

An inorganic fiber board having improved high resistance to splitting the board parallel to the plane of the board and an apparent density of from about 0.3 g/cm3 to 1.0 g/cm3 is produced by mixing 100 weight parts of an inorganic material consisting of 40-98 weight parts rock wool or slag wool, 2-30 weight parts asbestos and 0-50 weight parts of an inorganic filler with a binder of an aqueous emulsion of 3-25 weight parts (based on 100 weight parts of inorganic materials) of a thermosetting resin and 0.3-10 weight parts of a thermoplastic vinyl resin to obtain a slurry; dewatering the slurry on the screen to obtain a wet laid mat; and then drying and curing the mat to convert the thermosetting resin to an insoluble and infusible state. A surface decorated board is obtained by mixing vermiculite particles in the inorganic material. Another embodiment of a surface decorated board having a fine uneven crepe like pattern is obtained by rubbing the surface of a wet laid mat and applying suction to the other side of the mat repeatedly.

United States Patent [1 1 Kurashige et al.

[451 Apr. 16, 1974 [75] Inventors: I-Ilrotoshi Kurashlge; Klyonobu Fujii, both of Kurashiki, Japan [73] Assignee: Kuraray Co., Ltd., Kurashiki City,

Japan 22 Filed: July 26,1971

21 Appl. No.: 166,307

[30] Foreign Application Priority Data July 29, 1970 Japan 45-66218 [52] US. Cl 162/109, 162/134, 162/145, v162/152, 162/153, 162/155, 162/162,

[51] Int. Cl. D2lh 3/36, D2lh 3/50 [58] Field of Search 162/145, 152, 155, 162, 162/165, 168, 111, 164, 225, 222, 305, 362, 210,205, 109, 134, 153, 181 R, 116

[56] 1 References Cited UNITED STATES PATENTS R27,l09 3/1971 -Videen....' 162/109 X 2,395,375 2/1946 Linzell 162/134 X 2,225,585 12/1940 Devereux 162/116 3,365,358 l/l968 l-lutchins 162/155 2,992,963 7/1961 Nagel et al.... 162/168 2,732,295 1/1956 Hollenberg 162/152 X 2,633,433 3/1953 Hollenberg 162/155 X 2,338,839 l/l944 Coss 162/152 3,386,879 6/1968 Yan et al. 162/165 X 1,919,697 7/1933 Groff 162/168 1,548,790 8/1925 Lorenz l62/1ll 3,244,632 4/1966 Schulz et al. 162/145 X 1,698,298 l/l929 Clapp 162/162 X Primary Examiner-S. Leon Bashore Assistant Examiner-Richard H. Tushin Attorney, Agent, or Firm-Stepno, Schwaab & Linn [5 7] ABSTRACT An inorganic fiber board having improved high resistance to splitting the board parallel to the plane of the board and an apparent density of from about 0.3 g/cm to 1.0 g/cm is produced by mixing 100 weight parts of an inorganic material consisting of 40-98 weight parts rock wool or slag wool, 2-30 weight parts asbestos and 0-50 weight parts of an inorganic filler with a binder of an aqueous emulsion of 3-25 weight parts (based on 100 weight parts of inorganic materials) of a thermosetting resin and 0.3-l0 weight parts of a thermoplastic vinyl resin to obtain a slurry; dewatering the slurry on the screen to obtain a wet laid mat; and then drying and curing the mat to convert the thermosetting resin to an insoluble and infusible state. A surface decorated board is obtained by mixing vermiculite particles in the inorganic material. Another embodiment of a surface decorated board having a fine uneven crepe like pattern isobtained by rubbing the surface of a wet laid mat and applying suction to the other side of the mat repeatedly.

10 Claims, No Drawings INORGANIC FIBER BOARD WITH BINDER OF THERMOSETTING RESIN AND THERMOPLASTIC VINYLIC RESIN This invention relates to an inorganic fiber board containing slag wool or rock wool, and to a wet process of producing the same.

The object of the present invention is to provide an inorganic fiber board which possesses high resistance to split out parallel to the plane of the board.

One of the objectsof the present invention is to provide an inorganic fiber board useful for a wall board.

A further object of the present invention is to provide a decorative inorganic fiber board which has particles of vermiculite on the surface of the board.

Another object of the present invention is to furnish a decorative inorganic fiber board which has a crepe like patterned surface on the board.

An inorganic fiber board comprising a mineral wool, such as rock wool or slag wool, bound said fibers with a thermosetting resins, such as urea-formaldehyde resin, phenol-formaldehyde resin or malamineformaldehyde resin is disclosed in U.S. Pat. No. 2,633,433. A wet process of producing such a board is disclosed in Pat. No. 2,732,295..

These inorganic fiber boards have relatively low density, i.e., an apparent density of about 0.1 to 0.4 g/cm, relatively high flexural strength, water proof, fire proof and high electrical and thermal insulating properties. Therefore these boards are used as acoustical panelsor sheets'in ceilings.

But as these boards are formed from a water suspension of the mineral wool and the binder, the major proportion of the fibers therein are oriented in a plane substantially parallel to the plane of the board. Therefore, the layer of these boards are readily split out parallel to the plane of the board by a weak force.

This defect is caused by the migration of binder resin to the outer surface during the drying cycle of the wet sheet, and this migration results in a product that has a strong outer crust but a weak inner core. This phenomenon is considerably reduced by including a natural clay, such as bentonite and kaolin in the fiber board. But this method does not entirelyv prevent this phenomenon, therefore, these boards are limited to use as acoustical ceiling panels.

On the other hand, it is alsoknown to make inorganic fiber boards comprising a mineral wool, such as rock wool or slag wool with such fibers bound with starch, such as gelatinized starch. These boards are also used principally for acoustical ceiling panels, but these panels have a tendancy to sag in a high humid atmosphere.

The present invention relates to an improved inorganic fiber board having resistance to split out parallel to the plane of theboard and resistance to sag in a high humid atmosphere. Therefore, the board of the present invention is useful not only as a ceiling panel but also as a wall board in a room.

Under the investigation of the present inventors, it was found that these defects'of the prior art can be prevented combining a water insoluble thermoplastic vinyl polymer resin with a thermosetting resin as the binder for the mineral wool fibers. In the practice of the present invention, the thermosetting resins are usually dissolved or dispersed in a water suspension of mineral wool, and the water insoluble vinyl polymer resins are dispersed in the water suspension of mineral wool.

The inorganic fiber board of the present invention consists of the following ingredients:

(1) Inorganic materials rock wool or slag wool asbestos inorganic filler Binder resins a thermosetting resin (water-soluble or water-insoluble) a thermoplastic vinyl polymer resin (water-insoluble) 0.3 l0 weight parts The apparent density of the inorganic fiber board of the present invention may be regulated in the range of about 0.3 g/cm to 1.0 g/cm". A board having a density of about 0.5 to 1.0 g/cm is preferred for use as a wall board, since this board has improved impact strength and high bend modulus.

The mineral wool used in the present invention may be rock wool or slag wool, either long-fibre or loose wool, or what is known in the trade as granulated or nodulized wool.

As the asbestos used in the present invention, asbestos fibers known as chrysotile in the range of 5 to 7D may be used.

The effect of the blend of asbestos in the mineral wool is not only to produce inorganic fiber board with improved tensile strength and impact strength but also to promote the dispersion of the inorganic filler in the present inorganic fiber board. This effect is obtained by the adsorption force of asbestos to the inorganic filler and the filtering of the inorganic filler with asbestos in the step of dewatering the aqueous suspension. Therefore, the amount of asbestos must be regulated with the amount of the inorganic filler. The amount of asbestos in the practice of this invention may be in the range of about 2 to 30 parts by weight. If the amount of asbestos is increased to more than 30 parts, dewatering of the mineral fiber suspension on the screen is more difficult.

The inorganic filler used in the present invention may be powders of calcium carbonate, plaster and gypsum, slag, fly-ash, silica, sericite, natural clay, such as kaolin, bentonite or acid clay, or calcium silicate.

In the preferred embodiment of the invention, calcium carbonate, plaster and gypsum, slag, fly-ash, silica or sericite is employed so that the inorganic fiber board will have high impact strength. Heavy calcium carbonate or precipitated calcium carbonate is especially preferred. But in the present invention, portland cement or diatom aceous earth is not preferable as the inorganic filler.

The presence of the inorganic filler in the finished mineral wool board, which filler is dispersed among the mineral wool, serves to enlarge the contact points or surfaces of the binder resin with the mineral wool fibers. Accordingly, the strength of the finished mineral wool fiber board is improved.

Therefore, there may be obtained a relatively thin board having a thickness of about 4 to 8 mm with relatively high flexural strength and impact strength. But when the amount of the inorganic filler in the finished product is in excess of 50 parts by weight, the density of the product is too large for a wall board or ceiling board and the impact strength of the product is decreased.

ln the practice of the present invention, if desired, a minor amount of glass fibers may be used. The fiber length of the glass fibers is in the range of about 3 to 13 mm and the amount of the glass fibers in the board may be in the range of 0.5 to 30 weight parts.

As the thermosetting resin used in the invention, urea-formaldehyde resin, phenol formaldehyde resin, or melamineformaldehyde resin may be used. These thermosetting resins are in the initial stage of polymerization, and are curable by heat to insoluble and infusible resins.

As the water-insoluble thermoplastic vinyl polymers used in the invention, polyvinyl acetate, vinyl acetateethylene copolymer, vinyl acetate-acrylonitrile copolymer, vinyl acrylate copolymer, vinyl acetate-ethyl acrylate copolymer, vinyl acetate-methylmethacrylate copolymer, and acrylic polymers may be used.

The thermosetting resin is the predominant ingredient of the binder. This resin serves to improve the tensile strength, flexural strength, rigidness, hardness, and water-resistance and high humidity-resistance properties of the finished board. But when only this resin is used as the binder, the finished board is readily split or peeled out parallel to the plane of the board by even a weak force.

To prevent this phenomenon, it is necessary to use a minor amount of the water insoluble vinyl polymer resin with the thermosetting resin. These water insoluble vinyl polymer resins are usually available as an aqueous emulsion.

The amount of the thermosetting resin used in the binder may be in the range of about 3 to 25 weights parts by weight based on the inorganic material, which is the total weight of the mineral wool, asbestos and the inorganic filler. If the amount of the thermosetting resin is in excess of 25 parts, the fire resistance of the board decreases and the excess of the resin does not act to promote the binding effect of the mineral wool.

The amount of the water insoluble vinyl polymer resin used in the binder may be in the range of about 0.3 to weight parts based on the weight of the inorganic materials.

in this invention, known binders used for the production of mineral wool boards may be used as a supplemental ingredient of the binder of the invention. These supplemental binder ingredients include, for example, polyvinyl alcohol, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, the salts of polyacrylic acid, water soluble starch, starch, gum arabic, gelatine, glue and casein. These water soluble ingredients act as thickeners or protective colloids.

The amount of these ingredients used is below about 4 weight parts based on the inorganic material.

The product of the present invention may be prepared by any process in which a thermosetting resin and a thermoplastic vinyl polymer in the presence of an aqueous medium is incorporated with inorganic fibrous material, the fibers of which are interfelted in an aqueous suspension thereof and in which the resin after its association in the interfelted web is converted by heat to the infusible, insoluble stage.

in the preferred process of the invention, the board, which is subjected to heat to convert the thermosetting resin, is formed from an aqueous suspension of the inorganic fibrous material by the use of a screen to remove water therefrom. Preferably, the inorganic fibrous materials are mixed with an aqueous medium containing a dissolved thermosetting resin and a dispersed thermoplastic vinyl polymer or a synthetic rubber polymer. The mixing may be accomplished, for example, in a beater or a mixing or agitating tank or a head box, and the aqueous suspension containing the inorganic fibrous material and resinous binders is dewatered by the use of a screen. The resulting suspension may then be deposited either continuously on a conveying system or batchwise into the wet laid mat.

One of the surface decorated inorganic fiber boards of the present invention may be prepared by adding and dispersing vermiculite particles in the aqueous suspension of inorganic fibrous materials and the resinous binders, and treating said aqueous suspension by the above noted process. As the vermiculite particles are a mixture of various colored particles such as gold, silver, black brown and yellow ocher, the product board has various colored dots randomly disposed on a white gray surface background.

The particle size of vermiculite used in the present invention are in the range of passing 5 mesh sieve but being retained on mesh sieve, especially in the range of passing 10 mesh but retaining 50 mesh sieve. Particles below 80 mesh are not suitable to prepare the decorated board having the colored dots. The content of vermiculite particles in the board may be in the range of about 0.5 to 15 weight parts based on the total weight of the inorganic materials. When the content of vermiculite particles is more than about 15 weight parts, the appearance of the board surface is too loud and the mechanical strength of the board has a tendency to decrease.

Another embodiment of a surface decorated inorganic fiber board of the present invention may be prepared by the combination of the steps of sucking by a reduced pressure the water involved in the wet laid mat and rubbing the surface of the wet laid mat with the surface of the roll repeatedly.

By repeating the above noted combination of steps, for example, from two times to six times, the surface of the board has uneven wrinkles resembling the surface of crepe fabrics, such as crepe de Chine, sakker or voile.

When a minor amount of coloring agent such as a lake or pigment is added during the production of this board, most of the coloring agent migrates on to the hills of the wrinkles and the valleys of the wrinkle lack the coloring agent. Therefore, the surface of the board has colored hill parts of the wrinkles and non-colored (white gray) valley parts of the wrinkles. The product board, thus obtained, has a good appearance and is useful for a decorative wall board.

The present invention is illustrated by the following examples in which, unless otherwise specified, all parts are by weight.

EXAMPLE 1 One hundred parts of inorganic material consisting of 53 parts of slag wool, 17 parts of asbestos (10 parts of chrysotile 7 D and 7 parts of chrysotile 6 D) and 33 parts of precipitated calcium carbonate powder were mixed into 1,150 parts of water containing 13 parts of urea-formaldehyde resin, 0.9 parts of vinyl acetateethylene copolymer (ethylene content: 30 mol percent) and 0.6 parts of polyvinyl alcohol having a polymerization degree of 1,700 to produce a mineral wool suspension.

The suspension was mixed with a beater to produce a homogenized slurry. The slurry was dewatered on a screen of 80 mesh size to produce a wet laid mat. This mat was further dewatered with a press roll and suction to a water content of about 100 weight percent based on the solid ingredients. The mat was dried at 60 C and then cured with heat under a pressure of 0.1 kg/cm and a temperature of 160 C for 7 minutes.

In the process of producing the board, per cent of calcium carbonate and a minor amount of vinyl acetate-ethylene copolymer were lost by dewatering.

The board, thus obtained, was a light gray colored rigid board and has a thickness of about 7 mm., an apparent density of about 0.6 g/cm bend break strength of about 26 kg., bend modulus of about 80 kg/cm tensile strength of about 40 kg/cm and an impact strength of 0.20 ft. lb/in.

The board possesses high tenacities compared with the usual rock wool board. Therefore, this board can be used as a wall board, and this board better permits the making of large panel board units of dry board by cutting the board into the panels, such as 3 x 6 foot size.

On the other hand, a rock wool board produced by the usual known method compensates for low bend modulus and tensile strength by increasing the thickness of the board up to about 9 to 18 mm. But these thickened boards usually possess only a bend modulus below 40 kg/cm (most of them below 30 kg/cm) and tensile strength of 20 kg/cm (most of them below 10 kg/cm .The bend breaking strength and the bend modulus were measured by the test of The method of bending test for building boards J IS-A-l08 (1964) which is investigated by Japanese :lndustrial Standards Committee. 1

EXAMPLE n One hundred parts of inorganic material'consisting parts of slag wool, 15 parts of asbestos (chrysotile 7 D) and 30 parts of heavy calcium carbonate fine powder were mixed into 1500 parts of water to obtain a mineral wool suspension. Fourteenv parts of ureaformaldehyde resin were dissolved into said suspension, and then four parts of ethylene-vinyl acetate resin (Trade name: PANFLEX OM-4000) were added into said suspension to prepare the slurry.

The slurry was dewatered on a screen of 50 mesh size to prepare the wet laid mat. The mat was further dewatered with suction under a reduced atmosphere and pressed with rolls to a water content of about weight per cent. The mat wasdried at C and cured at 170 C for 25 minutes.

The board, thus obtained, has a crepe like patterned surface and an apparent density of about 0.65 g/cm.

The tearing strength parallel to the plane of the board of this example was 2.8 kg'lcm On the other hand, the tearing strength of a comparison board which was produced by the same process but without adding the ethylene-vinyl acetate copolymer resin was only 0.4 kg/cm As seen from the above comparison, ethylene-vinyl acetate copolymer, which is one'of the waterdnsoluble vinyl resins, remarkably increased the tearing strength parallel to the plane of the board.

EXAMPLE Ill 70 parts of slag wool, 30 parts of asbestos and 18 parts of powdered aluminum oxide (Trade name: almina white, made by Daimei Chemical Company) were mixed into 1,000 parts of water. The mixture was homogenized with a beater to obtain a suspension. 23 parts of phenol-formaldehyde resin (novolak type aqueous emulsion) and 5 parts of ethylene-vinyl acetate copolymer were dispersed in the suspension to obtain the slurry. The slurry was dewatered on a 50 mesh screen to prepare the wet laid mat. The mat was further dewatered'with suction under a reduced pressure and lightly pressed with rubber rolls to a water content of weight per cent. The mat on the screen was dried at a temperature of 90 C and removed from the screen. The dried mat was then cured at C for 20 minutes.

The resulting board had the following properties:

(After 24 hours in 20C water) The content of the phenol-formaldehyde resin in the board 11 weight per cent EXAMPLE iv.

55 parts of slag wool, 15 parts of asbestos (chrysotile 7 D), 7 parts of vermiculite (particle size 10 30 mesh) and 23 parts of calcium carbonate were dispersed in 1,150 parts of white water containing 14 per cent of urea-formaldehyde resin, 1 per cent of polyvinyl alcohol (polymerization degree 1700), and 1 per cent of ethylene-vinyl acetate copolymer (ethylene content 30 mol per cent), and beaten to obtain a homogeneous slurry.

Then, the slurry was dewatered on a screen having the 80 mesh size to make a wet laid mat. The wet laid mat was dewatered and pressed by sucking and pressing. The sheet material was removed from the screen and dried at 70 C and further cured at low pressure and C. The obtained board had a thickness of about 7 mm, and an apparent density of 0.5 g/cm. The surfaces of this board was decorated with vermiculite particles having various colors, such as gold, silver-like, black and brown which are scattered on a gray-white board.

The strength of this board was enhanced by adding only 3 to 4 parts of glass fibers to the slurry without changing the decorative appearance of the board.

Embossing may be applied to the wet laid mat and the thus obtainedboard has decorative embossing and the pattern of the vermiculite particles.

EXAMPLE V 80 parts of slag wool, 10 parts of chrysotile 6 D asbestos and 10 parts of vermiculite were mixed into 1,150 parts of water having 10 parts of urea-formaldehyde resin, 0.8 parts of vinyl acetate-ethylene copolymer (ethylene content: 33 mol per cent) and 0.8 parts of polyvinyl alcohol to produce a slurry.

This mixture was beaten with a beater to obtain a homogeneous slurry. This slurry was dewatered on a screen of 80 mesh size to produce a wet laid felt, and then this wet laid mat was dewatered by suction and by press-roll. This mat was dried at 60 C and the ureaformaldehyde resin in the mat was cured under a pressure of l kg/cm and a temperature of 160 C for 10 minutes.

The surfaces of the board were decorated with vermiculite particles forming golden, silver-like, black and brown dots on the white surfaces.

EXAMPLE VI 55 parts of slag wool, 15 parts of asbestos (chrysotile 7 D) and 30 parts of heavy calcium carbonate fine powder were mixed in white water containing 180 parts of urea-formaldehyde resin, parts of ethylene-vinyl acetate copolymer (ethylene content: 30 mol per cent) 0.3 part of powdered aluminum metal (coloring agent, particle size 1 10 p.) and 1,150 parts of water, and beaten to provide a homogeneous slurry.

The slurry was filtered on a 80 mesh screen to remove water in order to make a wet laid mat.

After the upper surface of the mat was smoothened with a rubber roll four times, the mat was sucked from the screen side to remove the water contained in the mat and the water content in the mat was regulated to about 100 weight per cent based on the total weight of slag wool, asbestos and calcium carbonate.

Then the mat was removed from the screen and dried at 80 C and further heated at 150 C for minutes to cure the urea-formaldehyde resin.

The board, thus obtained, had a thickness of 7.0 mm., an apparent density of 0.65 g/cm, and a decorative surface like a crepe de Chine pattern. The convex parts of the said pattern were colored gray with powdered aluminum metal and the valley parts of the said pattern were colored white gray. This board is useful for a decorative wall board.

EXAMPLE VII 54 parts of slag wool (granulated wool), 16 parts of asbestos (chrysotile 7 D), 28 parts of heavy calcium carbonate fine powder and 2 parts of glass fibers (fiber length: 6 mm) were mixed into an aqueous emulsion containing 160 parts of urea-formaldehyde resin, 4 parts of ethylene-vinyl acetate copolymer (ethylene content: 40 mol per cent), 0.10 part of inorganic pigment (brown), 0.025 part ofinorganic pigment (black) and 1,150 parts of water, and made into a slurry by the same process described in Example VI.

A wet laid mat was produced from a slurry by the same process described in Example V1.

The steps of rubbing the surface of the wet mat with the surface of the roll and sucking and dewatering the wet mat were repeated for three times, respectively. Then the mat was removed from the screen and dried at 70 C and cured at 150 C for 15 minutes.

The surface of the board had a fine uneven pattern like the surface of crepe de Chine fabrics.

EXAMPLE Vlll A board was produced by the same process described in Example Vll from inorganic materials consisting of 77 parts of rock wool (granulated white wool), 20 parts of asbestos (the same as in Example VII) and 3 parts of vermiculite particles.

The surfaces of this board had a fine uneven pattern like the crepe de Chine fabrics and vermiculite particles are dispersed on the surfaces.

What is claimed is:

1. An inorganic fiber board having an apparent density of about 0.5 g/cm to 1.0 g/cm and being highly resistant to splitting in the plane of said board, one of the surfaces of said board having a wrinkled surface, said board comprising:

i. weight parts of inorganic materials comprising from 40 to 98 weight parts of rock wool or slag wool, from 2 to 30 weight parts of asbestos, and from 0 to 50 weight parts of an inorganic filler, and

ii. a binder consisting of from 3 to 25 weight parts,

based on 100 weight parts of the inorganic materials, of a thermosetting resin, and from 0.3 to 10 weight parts based on the 100 weight parts of the inorganic materials, of a synthetic water-insoluble thermoplastic vinylic polymer, said rock wool or slag wool forming an interfelted web, said inorganic filler being dispersed in and around the interfelted web, and said wool fibers being bound by the cured thermosetting resin and the synthetic waterinsoluble thermoplastic vinylic polymer.

2. An inorganic fiber board according to claim 1, wherein said thermosetting resin is selected from the group consisting of phenol-formaldehyde and ureaformaldehyde resin.

3. An inorganic fiber board according to claim 1, wherein said synthetic water-insoluble thermoplastic vinyl polymer is ethylene-vinyl acetate copolymer.

4. An inorganic fiber board according to claim 1, wherein said synthetic water-insoluble thermoplastic vinyl polymer is selected from the group consisting of polyvinyl acetate, vinyl acetate-ethylene copolymer, vinyl acetate-acrylonitrile copolymer, vinyl acrylate copolymer, vinyl acetate-ethyl acrylate copolymer, vinyl acetate-methylmethacrylate copolymer, and acrylic polymers.

5. An inorganic fiber board according to claim 1, further comprising a minor amount of vermiculite particles randomly dispersed throughout said board.

6. An inorganic fiber board according to claim 1, further comprising a minor amount of a coloring agent and wherein said coloring agent is concentrated in the crest portions of said wrinkles thereby producing colored crest portions and non-colored trough portions thereof.

7. A process for producing an inorganic fiber board which comprises:

i. mixing 100 weight parts of an inorganic material comprising from 40 to 98 weight parts of rock wool or slag wool, from 2 to 30 weight parts of asbestos, and from 0 to 50 weight parts of an inorganic filler, with an aqueous emulsion of from 3 to 25 weight parts, based on 100 weight parts of the inorganic materials, of a thermosetting resin, and from 0.3 to 10 weight parts, based on 100 weight parts of the inorganic materials, of a synthetic water-insoluble thermoplastic vinylic polymer to produce a slurry;

ii. dewatering said slurry to produce a wet laid mat;

iii. repeatedly rubbing one face of the wet laid mat with a roll and applying a vacuum to the opposite surface of the mat; and

iv. drying said mat and then curing the thermosetting resin in the mat to an insoluble and infusible state, whereby there is produced an inorganic fiber board having high resistance to splitting parallel to the plane of the board and having a wrinkled surface.

9. The process for producing an inorganic fiber board according to claim 7, wherein said thermosetting resin is selected from the group consisting of phenolformaldehyde and urea-formaldehyde resin.

10. The process for producing an inorganic fiber board according to claim 7, wherein said synthetic water-insoluble thermoplastic vinylic polymer is ethylenevinyl acetate copolymer. 

2. An inorganic fiber board according to claim 1, wherein said thermosetting resin is selected from the group consisting of phenol-formaldehyde and urea-formaldehyde resin.
 3. An inorganic fiber board according to claim 1, wherein said synthetic water-insoluble thermoplastic vinyl polymer is ethylene-vinyl acetate copolymer.
 4. An inorganic fiber board according to claim 1, wherein said synthetic water-insoluble thermoplastic vinyl polymer is selected from the group consisting of polyvinyl acetate, vinyl acetate-ethylene copolymer, vinyl acetate-acrylonitrile copolymer, vinyl acrylate copolymer, vinyl acetate-ethyl acrylate copolymer, vinyl acetate-methylmethacrylate copolymer, and acrylic polymers.
 5. An inorganic fiber board according to claim 1, further comprising a minor amount of vermiculite particles randomly dispersed throughout said board.
 6. An inorganic fiber board according to claim 1, further comprising a minor amount of a coloring agent and wherein said coloring agent is concentrated in the crest portions of said wrinkles thereBy producing colored crest portions and non-colored trough portions thereof.
 7. A process for producing an inorganic fiber board which comprises: i. mixing 100 weight parts of an inorganic material comprising from 40 to 98 weight parts of rock wool or slag wool, from 2 to 30 weight parts of asbestos, and from 0 to 50 weight parts of an inorganic filler, with an aqueous emulsion of from 3 to 25 weight parts, based on 100 weight parts of the inorganic materials, of a thermosetting resin, and from 0.3 to 10 weight parts, based on 100 weight parts of the inorganic materials, of a synthetic water-insoluble thermoplastic vinylic polymer to produce a slurry; ii. dewatering said slurry to produce a wet laid mat; iii. repeatedly rubbing one face of the wet laid mat with a roll and applying a vacuum to the opposite surface of the mat; and iv. drying said mat and then curing the thermosetting resin in the mat to an insoluble and infusible state, whereby there is produced an inorganic fiber board having high resistance to splitting parallel to the plane of the board and having a wrinkled surface.
 8. The process for producing an inorganic fiber board according to claim 7, further comprising adding a minor amount of coloring agent into step (i), whereby there is produced an inorganic fiber board having a wrinkled surface wherein said coloring agent is concentrated in the crest portions of said wrinkled surface producing crest parts of the wrinkles and noncolored trough parts of the wrinkles.
 9. The process for producing an inorganic fiber board according to claim 7, wherein said thermosetting resin is selected from the group consisting of phenol-formaldehyde and urea-formaldehyde resin.
 10. The process for producing an inorganic fiber board according to claim 7, wherein said synthetic water-insoluble thermoplastic vinylic polymer is ethylene-vinyl acetate copolymer. 